Way to keep lighting from lamps without influence from environmental textures
Not that I know of, however you can add a sphere, add the texture to it using a Diffuse material, and then disable the Shadows option.

Add a UV Sphere to your scene (Shift+A), and scale as desired (S). 

Now go into edit mode (Tab) and select all (A) and unwrap using sphere projection (U > Sphere Projection)



Now set up your material like this:



Now all you need to do is to disable the casting of shadows. Go to Object > Ray Visibility and disable the Shadow option and the Camera option.



If the reflections are not quite apparent enough you can try setting the material of the sphere to an Emission shader instead of Diffuse and tweaking the value. 

Here are my results:

Diffuse



Glossy